BIỆN PHÁP THI CÔNG HỆ ỐNG GIÓ

MOS, Biện pháp thi công đường ống gió, Cách thi công đường ống gió, áp dụng cho các Tòa nhà cao tầng, văn phòng cao ốc, trung tâm thương mại, nhà máy. Tài liệu dùng ngôn ngữ tiếng anh, phù hợp cho các Kỹ sư, Ban quản lý làm việc trong môi trường nước ngoài

Submission Ref 0002

:PSC-HK-MS-M-Date:14-Feb-15

Revision: Rev00

Prepare by : Checked by : Approved by : Consulted by:

NAME: Hong Soon

DATE :

TABLE OF CONTENTS

Date: 14-Feb-15 1

Revision: Rev00 1

1 INTRODUCTION 5

1.1 PURPOSE 5

1.2 SCOPE 5

1.3 EXCKUSION 5

2 GENERAL 5

2.1 PROGRAM 5

2.2 LOCATION – ADDRESS 6

2.3 APPROVALS 6

2.4 LABOUR RESOURCES 6

2.5 COMMUNICATION 6

2.6 SITE RESOURCES REQUIRED 6

2.7 TEMPORARY MATERIALS 6

2.8 PROTECTION 7

2.9 EQUIPMENT/TOOLS 7

2.10 HOT WORKS 7

2.11 CONFINED SPACE WORKS 8

2.12 EMERGENCY & SAFETY EQUIPMENT 8

2.13 MATERIALS REQUIRED FOR INSTALLATION 8

2.14 SCHEDULE OF DRAWINGS 8

2.15 SCHEDULE OF INSPECTION/T&C FORM 8

2.16 ATTENDEES 8

2.17 SAFETY BRIEFING 9

2.18 MITIGATION OF RISK 9

3 ACTUAL WORKS METHOD STATEMENT 9

3.1 DELIVERY AND STORE 9

3.2 HOW TO INSTALL DUCT 9

3.2.1 REQUIREMENTS OF TECHNICAL SPECIFICATIONS 9

3.2.2 RECTANGULAR DUCT CONSTRUCTION 14

3.2.2.1 MATERIAL THICKNESS 14 a) Low Pressure (500Pa or 2inch WG) 15

b) Medium Pressure (1000Pa or 4inch WG) 16

3.2.2.2 FLANGED CROSS JOINTS 17

3.2.2.3 STIFFENERS 18

3.2.2.4 INTERMEDIATE STIFFENERS 20

3.2.2.5 TIEROD ASSEMBLY 21

3.2.2.5 TURNING VANES 22

3.2.3 CIRCULAR (SPIRAL) DUCT CONSTRUCTION 23

3.2.3.1 MATERIAL THICKNESS 23

3.2.3.2 CIRCULAR DUCT CROSS JOINTS 24

3.2.4 DUCT HANGERS & SUPPORTS 25

4 APPENDIX 26

A IPC FORM 26

1.2 SCOPE

a) This is the Method Statement for Air Conditioning System

Ductwork fabrication standards and installation

b) The Technical Specifications Ductwork requires the ductwork

materials and construction to DW144, 1998 Edition or to SMACNA.c) This MOS will utilize the HVCA DW144 – Specification for Sheet

Metal Ductwork Low, medium and high pressure/velocity airsystems 1998 for cross reference

d) The Technical Specifications Ductwork requires air leak test

procedures to refer to DW143 – A Practical Guide to DuctworkLeakage Testing

1.3 EXCKUSION

Not application

2 GENERAL

2.1 PROGRAM

a) Ensure that the shop drawing used for the references at site is

approved for construction

b) Ensure that designated manpower to conduct works at site must

be properly trained and well oriented by the safety engineer

c) All lifting equipment, tools and mobile scaffolding to be used must

d) All staffs associated with the works shall be sufficiently

experienced

e) When the workers climb up the working platform, ladder, his

hands must be free

f) All materials to be used at site must be properly secured and

2.3.1 Materials of submission (Waiting for submission & approval)

2.3.2 Shop drawing (Waiting for submission & approval)

2.4 LABOUR RESOURCES

The ducting team will coordinate and carry out as below organization chart:

2.5 COMMUNICATION

Office mobile phone or walkie-talkie will be used during working time.

2.6 SITE RESOURCES REQUIRED

2.6.1 Temporary fire protection equipment – Not applicable.

2.6.2 Site electric panel should be needed as site condition.

d) Caution Tape – several rolls

e) Traffic control cones

r) Electric cable roll

s) Hand tools

2.10 HOT WORKS

Hot works comprise of the weling only and will be carried inaccordance with hanger, support weld instruction manual The hotwelding will be under tolerance clean workshop envirment toensure no risk of dirt containmination

Where such exothermic wielding works are in progress, fireextinguishers shall be provided at full times

When such exothermic welding is carried out, the workers shall beprovided with welding gloves

2.11 CONFINED SPACE WORKS

2.13 MATERIALS REQUIRED FOR INSTALLATION

2.13.1 GI sheet, fitting as elbow, tee, reducer, flange, pin, threaded

h) ST106_MECH_MVAC_BD_B202

2.15 SCHEDULE OF INSPECTION/T&C FORM

Refer to ITP form as the attached reference

2.16 ATTENDEES

a) Sub-contractor manager

b) Sub-contractor site manager

c) Main contractor MEP coordinator

d) Main contractor mechanical engineer

e) HKL M&E manager

2.17 SAFETY BRIEFING

The contents of this method statement shall from the basis of atoolbox talk for all operatives before the commencent of the suchworks

3 ACTUAL WORKS METHOD STATEMENT

3.1 DELIVERY AND STORE

Materials arrived to site shall be inspected and stored according tomanufacturer recommendations Materials shall be stored in thecovered and dry space During the receiving materials of duct,manpower shall be used to make GI sheet, duct The duct andaccessories shall be protected and covered with polythene sheetsbefore installation

3.2 HOW TO INSTALL DUCT

3.2.1 REQUIREMENTS OF TECHNICAL SPECIFICATIONS

 The following are extracted from the project TechnicalSpecifications Materials related specifications are not listed

herein as their conformance would be better dealt withwithin material catalog submissions.

 The Contractor shall provide and install all necessaryductwork, control, isolating and balancingdampers, fire dampers, smoke dampers, grilles and diffusers

to form complete air distribution systems as indicated on thedrawings

 All ductwork shall be constructed and erected to present arigid installation free from sway, drumming and movement.Ductwork shall be true-to-size and accurately aligned As far

as is practicable, longitudinal seams and joints in adjacentductwork sections shall be aligned, ly where permanentlyvisible after installation

 Cross-breaking and beading shall be permitted on velocity ductwork only, except where rigid externalinsulation is to be applied

low- Take-offs from the main ducts shall be conical, bell mouth,

or shoe type and as shown on the drawings Duct sizesquare take-offs will not be permitted

 All intake and discharge openings and louvers shall be fittedwith 10mm mesh wire screen in addition to grilles or louvers

at such locations

 Perforated rivets shall not be used in the manufacture orerection of ductwork The use of self-tapping screws shall berestricted to the completion of site joints in extremelydifficult locations only

 Ductwork supports shall be positioned close to dampers,diffusers and all similar equipment which must not besubjected to distortion, in addition to those hangers andsupports generally required for ductwork

 Allowances shall be made in ductwork construction forinstrument and controls connections Adequate localstiffening shall be incorporated to provide rigid mountings.All instrument and control element installations shall bedetailed, constructed and installed by this Contractor

 Where ductwork is defined as “fire rated”, it shall beconstructed from an approved system of ductwork toachieve the designated fire rating Unless stated otherwise,all fire ratings shall be a minimum of 2 hours

 As an alternative to duct construction from fire ratedmaterials, conventional ductwork, supports and connectionsetc may be clad with a fire rated material, in accordancewith an approved construction method and details toachieve the specified rating The composite system usedshall conform with and be tested by 3rd party.

 All joints on fire rated ductwork and cladding shall be sealedwith a silicone based sealant or approved equivalentsuitably rated to ensure it maintains integrity for theduration of the specified fire rating

 All gaps around fire rating where it passes through or abuts

a fire compartmentation wall shall be packed with mineralfiber insulation

 Transit damage shall be repaired on site prior to erection

 All seams shall incorporate sealant and be tightly formed.Edge sealant shall not be used

 Sealant shall be used between sheet and flange section incross joint assemblies

 Flanged joints shall be located at all plant and equipmentitems, at structural walls and floor slabs and elsewhere asspecified for disconnection purposes

 Tie rod stiffeners for rectangular and flat oval ducts shallhave internal nut and external nut, metal and compressiblewasher, unless otherwise specified

 All bends shall be 'easy' type except where specifiedotherwise

 Double skin turning vanes shall be fitted in short radius('hard') bends over 300mm deep and in all square bends

 All ductwork serving kitchens shall be formed from minimum

22 gauge stainless steel sheets to BS 1449 Part 2 Grade 304

or SMACNA All kitchen ductwork shall have continuouslysoldered seams and water tight construction Drained sumpshall be provided at all low points of duct risers andhorizontal ducts Sufficient quantity of air tight access doorsshall be provided as describe below Access doors shall haveequivalent thermal resistance as the main ductwork.Dampers and grilles for the kitchen ductwork shall also beconstructed of stainless steel

 All ductwork and associated air grilles serving wastewatertreatment plant shall be fiberglass duct with minimum 3 mmthickness The accessories for duct work shall be made ofstainless steel SS 304 Fibreglass duct shall be connected byoverlay or flange connection method according tomanufacture’s recommendation

 Flexible ductwork shall only be used as indicated on theDrawings

 Reinforcement of flexible ducts shall be carried over airterminal and rigid duct branch spigots and secured withworm-drive clips and sealant as recommended by themanufacturer Test holes shall be formed in rigid ductworkadjacent to flexible ductwork

 Flexible joints shall be 50mm minimum and 250mmmaximum lengths and shall not intrude into the airwayunder any condition Ductwork shall be supported andaligned to prevent undue stress in the flexible joint

 Ductwork shall not be suspended from other services andsupport systems Ductwork supports shall be clear of allother services and support systems

 Access openings shall be provided in ducting systemsadjacent to the following items of equipment and asindicated on the Drawings: fire dampers, smoke dampers,automatic temperature and humidity detecting equipment,

on each side of "in-line" cabinet fan', filters, heater batteries

 Where possible openings shall be 450 mm wide by 450 mmhigh or as recommended by manufacturers, with galvanizedmild steel cover plates The duct openings shall beadequately reinforced, with the access panel cover beingmade air tight by means of a rubber gasket Access panelsfor use with insulated ductwork shall also be insulated to thesame thickness as the ductwork Insulated access panelsshall be of double skin construction with insulation infill

 All access panels shall be leakage tested to DW/144standard and to the test pressure of the ductwork

 Control and regulating dampers in ductwork systems shall

be provided in locations indicated on the Drawings Damperslocated beyond reasonable access by ladder, staging, etc,shall be provided with substantial sheathed flexibleoperating gear extended to normal working height

 Splitter dampers to control and regulate the air flow insupply and return air ducts shall be provided in all branch-offducts and in positions indicated on the Drawings.

 Fire dampers shall be provided in any ductwork passingthrough each and every fire compartment wall

 Smoke dampers shall be provided in any ductwork toprevent transfer of smoke into any designated escape route

 Fire dampers and frames shall not be supported by adjacentductwork Fire dampers and frames shall always be setparallel to the plane of the wall or floor

 To facilitate testing, balancing and commissioning of thecomplete systems, test holes shall be provided in theductwork Test holes shall be provided in each branch and atfan intakes and discharges to enable a Pitot Traversemeasurement of airflow to be taken All test holes shall beprovided with rubber blanking plugs and provision shall bemade in the insulation to allow removal of these plugswithout disrupting the general vapour seal to the insulation.Access points/panels in the insulation shall be suitablymarked to identify the test points underneath

 Air leakage testing of ductwork shall be as follow:

a) High pressure ducts - all tested

b) Medium pressure ducts – 10% of the ductwork shall be selected at random and tested

c) Low pressure ducts – untested

 In the event of test failure of the randomly selected section,the Contractor shall select two further sections at random fortesting Where successive failures are identified theContractor is required to apply remedial attention to thecomplete ductwork system

 The Contractor shall provide documented evidence of thecalculations used to arrive at the allowable loss for the section

to be tested and the Project manager shall witness and signthe result of the test

 Where acoustic treatment is required, sound attenuators shall

be selected to achieve NC level required

 Note the specified noise levels are for noise from equipmentserving the specific room and this is considered thebackground level Noise from other equipment not serving thespecific room shall not cause on impact which audible andshall be at least 10 dB below the background noise level ofthe specific room.

 Insulated ducts shall be supported on the outside of theinsulation, with load spreading metal plates of suitable sizeand thickness between the insulation and supports to preventthe insulation being crushed

 The following insulation material shall be used for each kind ofducts as shown on the table below:

 Bends and fittings shall be formed from mitred and trimmedsections cut to ensure that a good contact with the surface to

be insulated is made

 Insulation covering shall be secured by the application of afirst grade adhesive solution to the duct with the coveringheld by wire loops set at centers not greater than 250mm

 The insulation shall be firmly embedded to the entire surface

of the duct using a noninflammable adhesive that iscompatible with the insulation and cover

 At dampers, test points, access doors, etc the insulation shall

be neatly finished and carefully sealed Access doors shall beinsulated as the ductwork

3.2.2 RECTANGULAR DUCT CONSTRUCTION